1 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
2 .\" and Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
3 .\" and Copyright (c) 2007, 2008 Michael Kerrisk <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
7 .\" manual provided the copyright notice and this permission notice are
8 .\" preserved on all copies.
10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" Modified by Michael Haardt <michael@moria.de>
28 .\" Modified 1993-07-21 by Rik Faith <faith@cs.unc.edu>
29 .\" Modified 1996-07-09 by Andries Brouwer <aeb@cwi.nl>
30 .\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
31 .\" Modified 1997-05-18 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
32 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
33 .\" 2007-07-08, mtk, added an example program; updated SYNOPSIS
34 .\" 2008-05-08, mtk, Describe rules governing ownership of new files
35 .\" (bsdgroups versus sysvgroups, and the effect of the parent
36 .\" directory's set-group-ID permission bit).
38 .TH CHOWN 2 2010-11-22 "Linux" "Linux Programmer's Manual"
40 chown, fchown, lchown \- change ownership of a file
42 .B #include <unistd.h>
44 .BI "int chown(const char *" path ", uid_t " owner ", gid_t " group );
46 .BI "int fchown(int " fd ", uid_t " owner ", gid_t " group );
48 .BI "int lchown(const char *" path ", uid_t " owner ", gid_t " group );
51 Feature Test Macro Requirements for glibc (see
52 .BR feature_test_macros (7)):
60 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
61 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
63 || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
68 These system calls change the owner and group of a file.
69 They differ only in how the file is specified:
72 changes the ownership of the file specified by
74 which is dereferenced if it is a symbolic link.
77 changes the ownership of the file referred to by the open file descriptor
83 but does not dereference symbolic links.
85 Only a privileged process (Linux: one with the
87 capability) may change the owner of a file.
88 The owner of a file may change the group of the file
89 to any group of which that owner is a member.
90 A privileged process (Linux: with
92 may change the group arbitrarily.
98 is specified as \-1, then that ID is not changed.
100 When the owner or group of an executable file are
101 changed by an unprivileged user the
105 mode bits are cleared.
106 POSIX does not specify whether
107 this also should happen when root does the
109 the Linux behavior depends on the kernel version.
110 .\" In Linux 2.0 kernels, superuser was like everyone else
111 .\" In 2.2, up to 2.2.12, these bits were not cleared for superuser.
112 .\" Since 2.2.13, superuser is once more like everyone else.
113 In case of a non-group-executable file (i.e., one for which the
117 bit indicates mandatory locking, and is not cleared by a
120 On success, zero is returned.
121 On error, \-1 is returned, and
123 is set appropriately.
125 Depending on the file system, other errors can be returned.
126 The more general errors for
131 Search permission is denied on a component of the path prefix.
133 .BR path_resolution (7).)
137 points outside your accessible address space.
140 Too many symbolic links were encountered in resolving
148 The file does not exist.
151 Insufficient kernel memory was available.
154 A component of the path prefix is not a directory.
157 The calling process did not have the required permissions
158 (see above) to change owner and/or group.
161 The named file resides on a read-only file system.
163 The general errors for
168 The descriptor is not valid.
171 A low-level I/O error occurred while modifying the inode.
182 4.4BSD, SVr4, POSIX.1-2001.
184 The 4.4BSD version can be
185 used only by the superuser (that is, ordinary users cannot give away files).
187 .\" SVr4 documents EINVAL, EINTR, ENOLINK and EMULTIHOP returns, but no
188 .\" ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions.
190 .\" SVr4 documents additional EINVAL, EIO, EINTR, and ENOLINK
191 .\" error conditions.
198 system calls supported only 16-bit user and group IDs.
199 Subsequently, Linux 2.4 added
204 supporting 32-bit IDs.
210 wrapper functions transparently deal with the variations across kernel versions.
212 When a new file is created (by, for example,
216 its owner is made the same as the file system user ID of the
218 The group of the file depends on a range of factors,
219 including the type of file system,
220 the options used to mount the file system,
221 and whether or not the set-group-ID permission bit is enabled
222 on the parent directory.
223 If the file system supports the
226 .IR "\-o\ bsdgroups" )
230 .IR "\-o\ sysvgroups" )
232 options, then the rules are as follows:
234 If the file system is mounted with
236 then the group of a new file is made
237 the same as that of the parent directory.
239 If the file system is mounted with
241 and the set-group-ID bit is disabled on the parent directory,
242 then the group of a new file is made the same as the
243 process's file system GID.
245 If the file system is mounted with
247 and the set-group-ID bit is enabled on the parent directory,
248 then the group of a new file is made
249 the same as that of the parent directory.
256 mount options are supported by ext2, ext3, ext4, and XFS.
257 File systems that don't support these mount options follow the
263 semantics are deliberately violated on NFS file systems
264 which have UID mapping enabled.
265 Additionally, the semantics of all system
266 calls which access the file contents are violated, because
268 may cause immediate access revocation on already open files.
270 caching may lead to a delay between the time where ownership have
271 been changed to allow access for a user and the time where the file can
272 actually be accessed by the user on other clients.
274 In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
276 did not follow symbolic links.
279 does follow symbolic links, and there is a new system call
281 that does not follow symbolic links.
282 Since Linux 2.1.86, this new call (that has the same semantics
285 has got the same syscall number, and
287 got the newly introduced number.
290 The following program changes the ownership of the file named in
291 its second command-line argument to the value specified in its
292 first command-line argument.
293 The new owner can be specified either as a numeric user ID,
294 or as a username (which is converted to a user ID by using
296 to perform a lookup in the system password file).
305 main(int argc, char *argv[])
311 if (argc != 3 || argv[1][0] == \(aq\\0\(aq) {
312 fprintf(stderr, "%s <owner> <file>\\n", argv[0]);
316 uid = strtol(argv[1], &endptr, 10); /* Allow a numeric string */
318 if (*endptr != \(aq\\0\(aq) { /* Was not pure numeric string */
319 pwd = getpwnam(argv[1]); /* Try getting UID for username */
328 if (chown(argv[2], uid, \-1) == \-1) {
340 .BR path_resolution (7),